Mobile device display or portion thereof with a graphical user interface



The FIGURE is a front view of a mobile device display or portion thereof with a graphical user interface showing the present design.

The broken line showing of the mobile device display or portion thereof with a graphical user interface forms no part of the claimed design. The broken line showing of the display screen or portion thereof and portions of the graphical user interface form no part of the claimed design. 

CLAIM The ornamental design for a mobile device display or portion thereof with a graphical user interface, as shown and described. 